Computing networks can include multiple devices including network devices such as routers, switches, and hubs, computing devices such as servers, desktop PCs, laptops, workstations, and peripheral devices, e.g., printers, facsimile devices and scanners, networked together across a local area network (LAN), a wireless local area network (WLAN), and/or wide area network (WAN).
Internet content and application providers usually place multiple copies of replicated servers with a unified domain name at data centers in distributed locations. One goal is to deliver content and applications quickly and accurately to a given client location. One challenge to doing so is to determine which server site is closest in proximity or lowest in latency to a given client. As many network applications rely on Domain Name System (DNS) address resolution, work has been conducted with DNS servers to resolve the domain names of content and application servers to IP addresses.
Global Load Balance (GLB) systems have been developed to select a server site for a client in view of response time and availability. Existing, commercially available GLB products rely on measurement methods or IP-geography mapping for site selection. However, due to network security and filtering, more and more local. DNS systems of clients do not respond to traditional measurement methods like ICMP (Internet Control Message Protocol), DNS, UDP (User Datagram Protocol), or TCP (Transmission Control Protocol) probe messages. Moreover, since mapping inaccuracy is a possibility, geographic distance may not reflect network proximity directly. As such, geographic-based mapping is used in GLB as an assistant for site selection.